Field of the Invention
The present invention relates to a fuel cell and a manufacturing method thereof, and more particularly to a fuel cell comprising a membrane electrode assembly (MEA) integrated with a gas diffusion layer (GDL) and to a manufacturing method thereof.
Description of the Prior Art
Recently, in order to solve environmental pollution problems caused by the use of petroleum resources and cope with the exhaustion of petroleum resources, research and development on new and renewable sources of energy as possible alternative energy to the petroleum resources has received a great deal of attention.
As used herein, the term “fuel cell” refers to an electrochemical device that converts chemical energy directly into electrical energy through an electrochemical reaction between hydrogen, contained in a hydrocarbon-based material such as methanol, ethanol or natural gas, and oxygen supplied from the outside.
Fuel cells are classified, according to the kind of electrolyte, into molten carbonate fuel cells (MCFCs), solid oxide fuel cells (SOFCs), phosphoric acid fuel cells (PAFCs), polymer electrolyte membrane fuel cells (PEMFCs), direct methanol fuel cells (DMFCs) and the like.
In particular, fuel cells for most purposes operate on the same general principle, but are distinguished from each other by the kind of fuel they use, their operating temperature, the kind of catalyst that is implemented or the kind of electrolyte that is supplied.
Polymer electrolyte membrane fuel cells have advantages over other types of fuel cells in that they have high power density and efficiency, low operating temperatures, and a fast start and response characteristics. Due to such advantages, polymer electrolyte membrane fuel cells can be used in various applications, including as a power source in a vehicle, distributed power sources for residential applications, power sources for various portable devices, etc.
Fuel cells are used to convert chemical energy, produced by oxidation of fuel, directly into electrical energy. In the fuel electrode (anode) of the fuel cell, the oxidation reaction of hydrogen occurs, and in the air electrode (cathode), the reduction reaction of oxygen occurs. The overall fuel cell reaction is an inverse of water electrolysis, which produces electricity, heat and water.
A fuel cell unit typically is made up of an electrolyte membrane, electrodes (anode and cathode), a gas diffusion layer (GDL) and a separator. Such fuel cell units are assembled to form a fuel cell stack.
A structure composed of electrodes attached an electrolyte membrane is referred to as a membrane electrode assembly (MEA). The electrolyte membrane of the MEA is made mainly of an ion conductive polymer. The material of the electrolyte membrane is required to have high ion conductivity, show a high mechanical strength at a humidity of 100%, and have low gas permeability, and high thermal and chemical stability.
Also, the GDL can serve as a passage that allows the hydrogen and air introduced from the separator to be finely diffused and supplied to the MEA, while supporting a catalyst layer, allowing electric current generated in the catalyst layer to move to the separator, and enabling produced water to flow out of the catalyst layer. The GDL are typically provided on the upper and lower surfaces of the MEA and are made of a material such as carbon felt, carbon paper or carbon cloth.
FIG. 1 shows an MEA structure fabricated using a conventional lamination technology. The MEA structure shown in FIG. 1 is formed by applying a polymer film sheet 20 to both surfaces of an electrolyte membrane 10, thermally compressing the applied film sheet 20, and coating a catalyst layer 30a on the surface of the thermally compressed film sheet 20 applied to both surfaces of the electrolyte membrane 10.
However, the MEA is very thin (50 μm or less), and thus can be damaged during transport. Particularly, when the alignment between the MEA and the GDL during lamination is poor, lamination quality can be deteriorated. Currently, in most cases, the GDL and the MEA are simply laminated by a thermal compression method.
This low quality lamination between the MEA and the GDL leads to the poor performance of fuel cells, and in severe cases, the fuel cells are classified as defective products, and thus the use and supply thereof are limited. Accordingly, there is an urgent need for a solution to this problem.
The foregoing is designed merely to aid in the understanding of the background of the present invention, and is not intended to mean that the present invention falls within the purview of the related art that is already known to those of ordinary skill in the art.